The proposed research continues investigation of the characteristics of otitis media. The project will systematically study the pathogenesis of the different types of otitis media (purulent, serous, mucoid and chronic). It is proposed that these different types of otitis media are a continuum of otitis media. An attempt will be made to develop a biologically meaningful classification of otitis media using the classifications delineated above. Studies are in progress and will continue with both human subjects and animal models (mostly cats and chinchillas). The major investigations include biochemistry, immunology and bacteriology of middle ear effusions. The role of infection, eustachian tube dysfunction and immune response of the middle ear cleft will be studied in both humans and animals. The sequelae of otitis media, granulation tissue, cholesteatoma, cholesterol granuloma, are also being investigated, again in humans as well as in the animal model. The studies to determine if sensorineural hearing loss in a late manifestation of otitis media is an important aspect of the project. Systematic audiologic studies with humans will be conducted. Also, otophysiologic studies with animals are underway and will continue to investigate round window membrane permeability changes. Effects of topical drugs (antibiotics and antibiotic vehicles) will be studied. The results of all of these experiments will further our understanding of the nature and course of otitis media, thereby improving the accuracy of diagnosis and leading to improved treatment and prevention.